Separately fired preheater for gaseous fluids with recirculation of gases of combustion



P. H. KARLSSON El AL 2.440.77 SEPARATELY FIRED PREHEATER FOR GASEOUS FLUIDSWITH RECIRCULATION OF GASES OF COMBUSTION Filed Aug. 8, 1945 Per Iii/mar lfa r/aaan ER/YES 7' H l 1/05 7770M IN V EN TOR.

' the furnace in communication with the cham-- as the casingoutlet'22 leading to the heat exchanger iaten ted May 4,1948 i I I 2 UNITED STATES PATENT- OFFICE SEPARATELY PREHEATER GAS EOUS FLUIDS WITH RECIRCULATION OF GASES OF COMBUSTION Per Hiimer Karlsson, Weiisville, and A. Lundstrom, Valley Stream, N.VY., assignorl to V TheAii-Preheater Corporation New York, N. Y.

Application August 8, 1945, Serial No. 609,578 5 Claims. (Cl, 126-110.)

I a 2 i v a The present invention relates to heat exbers i1 and I8, respectively, both rows of openchangers and particularly to apparatus for transings being located below the zone of combustion or source of waste heat. a some industrial processes require that a gaseing 22 that is alined with the gas inlet 23 of a ous medium be heated under circumstances where vertically arranged rotary, regenerative prefuel has to be burned especially for this p rpose heater 24 of the Liungstrom type such as shown because the heating gases cannot be derived from in Patent No. 1,652,025, dated December 6, 1927. a boiler or source of waste heat. However, the Th body of the air preheater 24 is vertically employment of a separately fired heat exchanger disposed in a position or at a level opposite the for this purpose presents the disadvantage that intermediate chamber I! and does not encroach the temperature of gases when burning fuel with substantially upon thespace opposite the upper normal excess air is too high to be handled by a 5 and lower chambers it and is so that with the heat exchanger of conventional type having me-. gas passage of the preheater contiguous to the tailic surfaces for transmitting heat from.the casing is the inlet'and outlet ducts 23, 21 leadheating medium to the gas that is to be heated. ing to the preheater rotor on the gas side may In order to lower the temperature of the gases I be disposed in alinement with openings formed to a point suitable to be passed through the pre-' in the casing l3 and leading to the chambers l8 heater it has been proposed to dilute the gases and I6, respectively. a with cold air or alternatively to reclrculate part Having passed over the heat transfer surface of the flue gases through the furnace. The recarried in the rotor of the preheater the cool circulation-of flue gases ordinarily requires the gases are discharged from the gas passage of provision of elaborate and expensive duct work 25 the preheater through the outlet 21 whichis to connect the outlet of the preheater with the I alined with an inlet opening 28 formed in the furnace for recirculating part of the gases and I casing is and leading to the upper chamber It. with a stack for disposing ofthe remainder. At -the other side of casing is (diametrically op- The present invention contemplates avoidance i posite as shown) an outlet opening 3| places the of the above disadvantagesby the provision of so chamber is in communication with a duct 32 a furnace and preheater so constructed and comleading to the suction side 33 of an induced draft pactly arranged as to minimize the amount of fan 34. A branchedoutlet duct is provided on duct work required. the discharge side of the fan 34, one branch 35 In the drawings: a leading to a stack- 36 while the branch 11 ex- Figure 1 is an elevational view partly i e 35 tends to an inlet opening at in casing is leading tion of a separately fired preheater embodying vt0 the intermediate chamber the present invention; and i y The air or'other g'aseous'fluid to be heated is vFigure 2 is a plan view of the apparatus illussupplied. by a forced draft fan 40 to the inlet 4| trated in Figure 1. l on the "air side .of the preheater and discharged Referring to the drawings. the numeral ill 40 through the outlet duct 42 into a conduit 43 that designates a furnace, preferably in the form of a extends to the point of use. The amount of gas vertically disposed cylinder, having one or more recirculated under the control of a damper 39 fuel burners ii in its top end wan .for mtroin the outlet duct for fan 34 is caused to enter ducing a fueland air mixture into the furna e the furnace In substantially uniformly circumferin adownward direction. Spaced outwardly from 45 entially of the furnace by having the openings the composite refractory and insulation wall i2 20 facing the gas return p 38 of a c nsi r ly oi the furnace is a, casing I; thu providing a, smaller size than those at the opposite side of space surrounding the furnace which is sub-- thefurnace so that some of the gas must flow divided by vertically spacedpartitions l4, II to through the chamber l1 and around the furnace form upper, intermediate and lower chambers i6, 5 to enter the latter at points spaced circumfer- I! and II, respectively. Above and below the V entially of the chamber as well as near the point 7 a partition ii are rows of ports or openings 20, and of admission thereto. For similar reason the 2i spaced circumferentially and arranged in rows openings 2| leading from the furnace it into the around the wall l2 and placing the interior of lower chamber is are smaller on the side facing the furnace on the side the side wall of said furnace;

' with cumferentially a substantially uniform mixhlre of 24. Thus, recirculated gases and products of effected in the furnace and this is aided by causing the greater proportion of the gases to leave remote from the heat exchanger and thereby avoiding an outrushlng of the gases through the openings on the right hand side directly facing the casing outlet openin ll.

What we claim is:

l. A separately fired heat exchange unit comprising; a vertically disposed cylindrical furnace having downwardly firing fuel burners in its uper end wall, a casin spaced radially outward of means closing the spaces between upper and lower ends of said casing and said furnacekvertically spaced partitlons dividing the enclosed space around said furnace into upper, lower and intermediate chambers, the wall of said furnace being formed circumferentially thereof with openings arranged in groups s aced axially or the furnace and placing it in communication with the lower and intermediate chambers; an indirect type heat exchanger mounted adjacent one side of said casing with the inlet and outlet of its heating medium disposed contiguous to said casing; an outlet for said lower chamber and an inlet for the upper chamber both formed in said casing on the side adjacent said heat exchanger; means connecting said outlet with the lower end and said inlet with the upper end of said heat assage; an outlet for said upper in said casing at the side opposite its inlet; an induced draft fan having its inlet connected with the outlet of said upper chamber; an inlet for said intermediate chamber formed in said casing at theside opposite said heat exchanger; a duct connected tothe discharge side of said fan having a pair of branches communicating respectively with a gas outlet for the inlet vto said interme-s the system and with diate chamber so arranged in conjunction thereas to direct part of the products of combustion that flow serially from the furnace through said lower chamber, said heat exchanger passage and said upper compartment, back into said fur- :nace via said intermediate chamber; and means for circulating a heat exchanger.

2. A separately fired heat exchange unit comprising; a vertically disposed cylindrical furnace having downwardly firing fuel burners in its upper end wall: a casing spaced outwardly from the side wall of said furnace and closed at its upper and lower ends; vertically spaced partitions dividing the enclosed space around said furnace into upper, lower and intermediate chambers, the wall of said furnace being formed cirfluid to be heated through said ranged in groups axially of the furnace and placing it in communication with the' lower and intermediate chambers; an indirect heat exchanger mounted adjacent one side of said casing .with the inlet and outlet of its passage for the heating medium disposed contiguous to outlet for said lower chamber and an tie upper chamber formed in said casing on the side adjacent said heat exchanger; means connecting said outlet with the lower end and said inlet with the upper end of said heat exchanger thereof with spaced openings arsaid casing; an

inlet I01- mbustionispassage for the 1 the inlet and outlet with spaced openings passage; an outlet for said upper chamber formed in said casing in circumferentially spaced relation to its inlet; an induced draft fan' having its inlet connected with the outlet of said upper chamber; an inlet for -.through said one chamber,

said intermedia te chambe formed in said casing adjacent said fan: a duct connected to the discharge side of said fan having a pair of branches communicating respective" ly with a gas outlet for the system and wi inlet to said intermediate chamber so arranged in conjunction products of combustion that fiow serially heat back into said furnace via sai chamber; damper means in said duct for regulating the volume of chamber. and means for circulating a fluid to be heated through said heat exchanger.

3. A separately flred heat exchange unit com prising; a furnaceha'ving fuel burners in an end wall thereof; a asing surrounding said furnace and spaced outwardly from its, side wall to enclose a space around said furnace, the wall of said furnace being formed circumferentially thereof with spaced openings arranged in axially spaced rows and placing said furnace in comwith said enclosed space; a partition located between said rows to form 'two contiguous chambers; an indirect heat exchanger mounted 'adiacent one side of said casing with lag medium disposed contiguous to said casing; an outlet for the one chamber remote from said fuel burners formed in said casing on the side adjacent said heat exchanger; means connecting said chamber outlet with the inlet end of said heat exchanger passage; an induced draft fan having its inlet connected to the outlet of said e; an inlet for said other, chamber formed in said casing adjacent said fan; a duct connected to the discharge side of said fan having a pair of branches communicating respectively with a gas outlet for the system and other chamber so arranged in conjunction therewith as to direct part of the products of combustion that flow serially from the furnace said heat exchanger passage, back into said furnace via said other chamber; damper means in said duct for regulating the volume of gas entering said other chamber; and means for c culating a fluid to be heated through said heat exchanger.

4. A separately fired heat exchange unit comprising; a vertically disposed furnace having downwardly firing fuel burners in its upper end circumferentlally thereof arranged-in axially spaced groups and placing said furnace in communication with said enclosed space; a horizontal parfurnace being formed tition located between said groups of openings and of said chambers formed in said casing adjacent said fan; a duct connected to the discharge side of said fan having a pair of branches communieating respectively with a gas outlet for the systherewith as to direct part of the gas entering said intermediate.

of its passage for'the heatwith the inlet to said casing with the inlet and outher: and means for circulating a fluid to be heated through said heat openings formed in portions side diametrically opposite said inlet respectively.

PER HILMER. KARL-880R.

6 summons mm The following references are of record in the tile of this patent:

NITED STATES PATENTS Number RNEST A. LUNDSTROM. 20

Name Date ll Apr. 29, 1884 Omalho Apr. 27, 1886 Russey Sept. 17, 1889 Cowles Dec. 5, 1905 Fahrenwald Sept. 14, 1928 Norton Nov. 28, 1944 l 

